Quote:
Originally Posted by iamnotahippee
To that end...if there was a way to go 4 wheel drum brakes, that would return the best mpg. Disc brakes are going to drag...period. They relay on the elasticity of a square cut o-ring to open the brakes up when they are released. Keeping all the friction surfaces and the caliper pins cleaned and lubed would be a good preventive maintenance along with checking all the rear drum brake gear.
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I'll concede that, all things being equal, disc brakes may have a touch more drag than drum brakes. And performing the maintenance items you mention is an excellent idea as well. But wheel bearings always have a bit of play and brake rotors always have a bit of runout, so brake pads are always going to be pushed back at least a bit from the rotor. Also considering the number and scale of other sources of friction in an automobile, disc brake drag is a pretty minor factor.
Drum brake drag from sticky cables however - I saw a *lot* of that in my mechanic days, and it can be considerable. Also folks should be aware that many cars with 4-wheel discs have separate drum brake assemblies, typically on the rear wheels, just for handbrake duties. Subarus for example have them inside the rear rotors. These tend to be ignored when servicing brakes and can be a source of drag just like a vehicle with rear drum brakes.